1. Field of the Invention
The invention relates to a noise removing circuit for removing impulse noise from a signal.
2. Prior Art
FIG. 7 shows a general construction of a prior art noise removing circuit for removing impulse noise from an input signal. In FIG. 7 when a noise detector 30 detects no impulse noise in an input signal, a switch 31 is closed so that the input signal is directed to an amplifier 33 which outputs an amplified signal. When the noise detector 30 detects an impulse noise in the input signal, the switch 31 is opened so that the voltage of input signal just before the switch 31 is opened is held across a capacitor 32. The amplifier 33 amplifies the voltage across the capacitor 32 and outputs the amplified voltage.
FIG. 6 shows the change in waveform of an input signal passing through the circuit in FIG. 7. As shown in FIG. 6, the prior art noise removing circuit is such that the voltage of the input signal just before an impulse noise is detected is held across a capacitor and is outputted during noise removing period. Thus, the output signal waveform is different from what would otherwise be present if impulse noise is not contained in the input signal. This causes the output signal to be distorted after impulse noise has been removed therefrom.